Optimizing preventive replacement schedule in standby systems with time consuming task transfers

In many industrial and technological systems, due to factors such as deterioration, corrosion, attacks, etc., preventive replacement is typically performed according to a predetermined schedule to renew the worn or aged online element using a standby element, enhancing the mission success probability. This paper models such a standby system with its mission time being divided into a certain number of mission parts (MPs). During different MPs, according to a pre-specified sequence, different system elements are activated to perform the mission operation. Upon completing each MP, following the preventive element replacement, a time-consuming transfer procedure must be conducted to start the new MP. The mission is successful when the last MP can be accomplished by an available system element. An event transition-based method is proposed to evaluate the mission success probability (MSP). The optimal preventive replacement scheduling problem is then solved, which finds the number of MPs and their durations maximizing the MSP. In the case of heterogeneous system elements, a combined optimization problem that finds the optimal element activation sequence and the optimal preventive replacement schedule to maximize the MSP is formulated and solved. Effects of several model parameters (the number of MPs, the number of system elements, task transfer time) are investigated through examples.